Containers can be tested for defects or the presence of foreign bodies in the container using ultrasonic testing. A variety of ultrasonic testing methods and equipment for ultrasonic testing of containers are described in the art, e.g., in U.S. Pat. Nos. 6,125,704, 5,955,670, 5,804,730, 5,089,997, 5,085,082, 4,658,649, and the references cited therein, as well as in recent applications of the inventors and their co-workers, e.g., U.S. Ser. No. 09/613,704; U.S. Ser. No. 09/613,705; U.S. Ser. No. 09/671,405 and U.S. Ser. No. 60/265,171.
Most gas cylinders today are retested with pressurized water (i.e., a “hydrotest”). This method checks expansion, which is related to wall thinning due to corrosion, but does not identify cracks, or other significant cylinder defects.
The present invention overcomes the limitations of the prior art by providing new ultrasonic methods and apparatus for testing cracks and other defects in pipes, cylinders and other containers.